Interference

[DG]

First, you can not protest a game based on an umpire's judgement. Second, only one fielder is afforded protection from fielder's interference. If the pitcher has the best chance he is protected. Third, you said the contact was incidental, but then said the catcher initiated the contact. Some might argue obstruction by the catcher, had the batter been knocked down by a catcher who initiated contact. This is one of those had to be there plays, to rule obstruction. But based on what you have written there is no interference by the batter.